Abstracts

To investigate whether the amount of interictal epileptic activity of temporal lobe epilepsy (TLE) correlates with the degree of metabolite alterations of ¹H-MR Spectroscopy (¹H-MRS). 30 controls and 42 consecutive patients diagnosed with TLE by clinical patterns and intensive video EEG monitoring were investigated by ¹H-MRS. Video-EEG registration was performed using the Glonner system (Munich, Germany). 32-64 EEG channels were used in order to record interictal and ictal epileptiform activity in temporal lobes. ¹H-MRS Single Voxel Spectroscopy of temporomesial regions was performed at 1.5 T.. Determination of absolute metabolite concentrations was carried out by water scaling. Hippocampal voxel were placed in a way to avoid susceptibility effects by covering most of the hippocampus and to minimize partial volume effects resulting from other neighbouring tissues. N-acetylaspartate + N-acetylaspartyl-glutamate (tNAA), choline (Cho), creatine (Cr), total glutamate plus glutamine (Glu+Gln) and myo-inositol (Ins) were quantified using LCModel, a frequency domain spectral fitting program. Results of ¹H-MRS were correlated to the findings of intensive video EEG monitoring. Interictal epileptiform discharges (IEDs) were calculated by the number of IEDs counted on either side as a percentage of the total number of IEDs recorded on both hemispheres. The localization to the temporal lobe was confirmed by ictal video recording.
Statistics: The degree of metabolite alterations was determined by z-scores. Pearson Correlation Coefficient was calculated between the degree of metabolite alterations and the degree of IEDs calculated as a percentage of the total number of EEG findings of both hemispheres. For all tests, statistical significance was accepted at p[lt]0,05. Spearman Rank Order Correlation Coefficient revealed a moderate correlation ([ndash]0.529; p=0.014) between the percentages of IEDs calculated as described above and the z-scores of tNAA reduction. Our results reveal that interictal spike activity in patients with TLE correlate with tNAA reduction. Considering that tNAA represents a marker of neuronal dysfunction, ¹H-MRS gives evidence of severity of neuronal dysfunction in patients with TLE reflected in increased interictal epileptic activity. (Supported by the Wilhelm Sander Foundation.)